What is an ultrasound scan?

An ultrasound scan involves transmitting high frequency sound waves through the uterus. These bounce off the baby and the returning echoes are translated by a computer into an image on a screen that reveals the baby's position and movements. Hard tissues such as bone reflect the biggest echoes and are white in the image, and soft tissues appear grey and speckled. Fluids (such as the amniotic fluid that the baby lies in) do not reflect any echoes so appear black. It is the contrast between these different shades of white, grey and black that allows your obstetrician to interpret the images.

Most parents look forward to their scan because it gives them the first glimpse of their baby. Your doctor will probably give you a printout of your baby as a keepsake. However, it is important to remember that the main purpose of the scan is not to provide the first photo for your baby album, or to find out your baby's sex, either. It is to check that your baby is growing and developing normally.

Is ultrasound safe?

Ultrasound has been used in pregnancy for nearly 30 years and medical research has found no side effects. No association has been shown between ultrasound exposure and the baby's birthweight, childhood leukaemias or other cancers, eyesight, hearing or dyslexia. Read more about scans and safety.

What is an ultrasound scan used for?

Depending on which stage of pregnancy they are done at, ultrasound scans can:

Who will do the ultrasound scan?

Scans are usually performed by your own obstetrician or a sonographer. Special scans may be required in some pregnancies and these will be performed by a doctor trained in ultrasound, known as a fetal medicine specialist.

How is the ultrasound scan done?

If you're having a scan in early pregnancy, you'll need to drink several glasses of water beforehand so that your uterus is pushed out of your pelvis by your bladder, allowing the doctor to get a good picture of your baby. She will put some (usually very cold!) gel on your tummy and will move a small hand-held transducer over your skin to get views of the baby.

If your baby is still too deep in your pelvis, or if you are overweight, the images will not be very clear, so a vaginal scan may be necessary. The vaginal transducer is long and narrow to fit inside your vagina. The doctor will use a probe cover (similar to a condom) and will lubricate this with plenty of gel so it slides in easily. It is not necessary to go in very deeply, and it will not harm you or your baby in any way. Vaginal scans give a much clearer picture of your baby, especially at a very early stage of pregnancy.

Does an ultrasound scan hurt?

An abdominal scan is painless except for the discomfort of the transducer pressing on your tummy if you have a very full bladder. A full bladder is not necessary for scans in later pregnancy.

One advantage of a vaginal scan is that it is best done with an empty bladder, so many women find this scan more comfortable than an abdominal one.

When are ultrasound scans usually carried out?

Health Ministry guidelines recommend a scan every four weeks until 28 weeks. Then you will be scanned every two weeks until your last month, when you will be scanned every week.

Do I have to have an ultrasound scan?

Although the vast majority of women in Malaysia who pay for private healthcare receive ultrasound scans, it is not compulsory. Mums who get their antenatal in government hospitals and clinics may get no or very few ultrasound scans.

Scans can give useful and reliable information about your pregnancy, and most women find them enjoyable and reassuring. However, many abnormalities cannot be seen on a scan, and sometimes the scan findings can cause uncertainty and anxiety.

The final decision whether or not to have a scan is entirely yours.

What if the ultrasound scan shows a problem?

You will naturally be very worried if your scan suggests that there is a problem with your baby. Sometimes a definite diagnosis can be made from the scan, such as spina bifida. In other cases the scan may show minor changes, known as "markers", which may be a sign of a more serious problem, such as Down's syndrome, or may turn out to be just a variation of normal. (Read more about ultrasound markers.)

If your doctor finds anything unusual when doing the scan, she may refer you to a fetal medicine specialist. It may be necessary for this doctor to perform a further test such as a CVS or amniocentesis to see if the baby's chromosomes are normal.

In the unlikely event that your baby does have a serious health problem, you will need time and support to think through your choices. These may include preparing for the birth of a baby who needs special care or, in rare cases, carrying out surgery on your unborn baby.

Talk to other mums-to-be about their ultrasound scans. You'll find them in our Pregnancy forum.

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